I have a Hampton Bay Ceiling fan that was working but I hit a blade with a folded towel swatting at a fly. After that it swings when turned on. How do I get it to balance again?

Turn off the fan. Check each individual blade with a screwdriver to make sure they are all 'tight'. If it still swings, you may have to retighten the screws that hold the fan motor.

XenoSapien

Um, no. The previous answer is wrong. You bent one of the blades when you swatted it. Balancing instructions are here:

Ceiling fan blade balancing issues - Ceiling Fans N More

Yes. Yes I do. That's why it says "expert" next to my name.

Awesome answer, ceilingfanrepair!! I had the same problem on a Hampton Bay fan and your advice was right on. Thanks a bunch!

Glad I helped :)